Two-stage pump, in particular a vacuum pump



Aug- 21, 1956 M. AUWA'RTER 2,759,66

TWOSTAGE PUMP, IN PARTICULAR A VACUUMPUMF F'iled May 6, 1950 fm enzor: 174x 0 Uta/15R FER United States Patent TWO-STAGE PUNIP, IN PARTICULAR A VACUUM PUMP Max Auwiirter, Iramaliustrasse, Balzers, Liechtenstein, assignor to Dr. Alois Vogt, Vaduz, Liechtenstein Application May 6, 1950, Serial No. 160,562

Claims priority, application Switzerland May 7, 1949 9 Claims. (Cl. 230-152) This invention relates to pumps, and more particularly to a high speed two-stage pump.

Vacuum pumps heretofore known as circular piston pumps have a cylindrical or slightly elliptical stator part in which an eccentrically mounted rotor operates. Depending on the particular type of circular piston pump, either vane-shaped slides are arranged in the rotor or the stator, or additional roller rings are provided which are rolled past along the wall of the stator and the slide.

In either case, the rotary parts of such pumps are never balanced with respect to the mass of the slides. For this reason the speed of the pumps cannot be increased at will and accordingly there is a practically constant ratio between the output of the pump on the one hand and the volumetric capacity and the speed on the other hand which cannot be improved by an increase of the speed.

It is an object of the present invention to provide means rendering it possible to increase the output of a circular piston pump by increasing the speed at which the pump is driven.

It is another object of the present invention to provide means facilitating the automatic guiding of slides in a pump of the aforesaid type whereby said pump is balanced with respect to the mass of the slides thereof.

It is a further object of the present invention to provide means facilitating the construction of a pump having an exceptionally high output capacity in comparison to its overall dimensions.

According to the present invention there is provided a pump which does not have the disadvantages mentioned and is in particular characterized in that a cylindrical stator space is subdivided in two pump spaces arranged in series by a cylindrically shaped annular rotor arranged eccentrically to said stator space, said rotor contacting simultaneously the inner and the outer wall of said stator space at one point each, said pump spaces in their turn being subdivided into, delivery chambers by means of slides arranged in said rotor and bearing against the walls of said stator space.

By way of example an embodiment of the present invention is illustrated in the drawing accompanying and forming part of this specification, in which:

Fig. 1 shows a vertical longitudinal section through a two-stage vacuum pump with vertical rotary shaft according to the present invention, the section being taken along lines II of Fig. 2 and Fig. 2 is a horizontal cross-section taken along lines II-II of Fig. 1.

Disposed within the inner space of a drum-shaped stator casing 1 and supported on a lower bottom or transverse wall thereof is a cup-shaped rotor 2 which is eccentrically mounted so that its outer cylindrical surface contacts the stator casing 1 at one point on its inner cylindrical surface. Traversing the stator 1 is a transverse cover wall 3 which dependingly carries a hollowcylindrical extension chamber or sleeve 4. The sleeve 4 extends into the interior of the rotor 2 and is arranged concentrically of the stator casing 1 and has a diameter selected so that its outside wall contacts the inside wall of the rotor 2 at one point thereof. Thus the cylindrical stator space located between the outer stator casing 1 and the inner stator part or extension chamber 4 is subdivided by the rotor 2 into two interspace chambers or pump spaces which are crescentshaped at A and B as seen in Fig. 2. Supported in the guiding slots of the rotor 2, are two slides 5 and 6 which are disposed radially of the rotor and are arranged for radial displacement. The slides 5 and 6 extend from the inside wall of the stator 1 through the outside wall of the rotor 2 and subdivide each of the two pump spaces into two delivery chambers. The end surfaces of the slides 5 and 6 which rest against the stator walls are rounded off into circular-cylindrical surfaces. As illustrated in Fig. 2 the two end surfaces of each one slide are defined by one and the same circular cylinder, the radius of which is equal to half the difference of the radii of the inner and the outer wall of the cylindricalannular stator space.

If the rotor is adapted for rotation in the direction of the arrow 7, the outer pump is provided with a suction inlet opening 8 which is connected to a suction pipe by means of a connecting pipe 9, whereas its delivery outlet 10 is in connection with an interspace 11 which is formed above the cover wall 3 by means of an insert 12 forming a transverse wall also connected to stator housing as is transverse cover wall 3. The inner pump has a suction inlet 13 which leads into the afore-mentioned interspace 11, whereas the delivery outlet 14 leads into an ejection space or chamber 15 provided above the insert or transverse wall 12 through a valve 23. The interspace 11 is similarly connected to this ejection space through a valve 16. A drip pipe 17 passes through transverse wall 12 and the cover wall 3 and further into the interior of the inner stator extension chamber or part 4 in which a flat pan or reservoir 18 is provided. Ducts 25 connect reservoir 18 with the space of the outer pump. An orifice or overflow 19 leads from the interior of the hollow-cylindrical chamber 4 to the suction side of the inner pump.

The ejection space 15 is partly filled with an oil bath 20 serving for sealing and lubricating the pump, said oil bath covering the two ejection valves 16 and 23 held in place by means of screws 16' and 23'. Through conduit means in the form of drip pipe 17 oil drips slowly into the reservoir 18 and from here through ducts 25 into the outer pump space (due to centrifugal force past the fine gap between stator 1 and rotor 2).

. During operation the outer pump sucks the fluid to be pumped through pipe 9 and the suction inlet 8 and forces the quantity of fluid conveyed through the ejection outlet 14) into the interspace 11 and from there through the valve 16 into the ejection space 15. If the suction pipe 9 is connected to a container to be evacuated the discharge pressure of the aforesaid quantity of gas or fluid progressively decreases with the increase of the vacuum in the container until this vacuum becomes insuflicient to contribute to a discharge pressure to open the ejection valve 16. Now the inner pump sucks off the gas from the interspace 11 through its suction inlet 13 and forces it through the ejection valve 23 into the ejection space 15. Together with the gas the two pumps simultaneously convey the oil contained therein, said oil reaching the ejection space 15'by passing from the outer pump through the inner pump and returning from there by way of the pipe 17 and the reservoir 18 back to the outer pump space.

The reservoir 18 located in the inner stator extension part 4 serves as a degasifying and regenerating device for the oil which in a thin layer in the tank is subjectedto the vacuum of the inner atmospheric-sided pump as the interior space of the part '4 is in connection "with the suction side of this pump by means of the aperture 19. This vacuum is sufficient to evacuatethe gas particles from the heated oil, the heatin'g of the oil being achieved automatically by the friction prevailing in "the pump. As this degasifying and regenerating device is located in the center of the pump a higher temperature prevails at this point than in the remaining parts of the pump and aids in the degasifying and regeneration of the oil and lessens the diffusing effect in the outer pump.

The vacuum pump shown is designed for a vertical rotary shaft, and the rotor 2 can be coupled with the shaft of a motor by means of the shaft '21 or canac'tua lly be the motor shaft. In the latter case the shaft 21 is vacuum-tightly mounted in the pump casing by means of a seal 22. In this vertical position the described vacuum pump is suitable for being fitted together with a diffusion pump located vertically below it under the boiler.

With the embodiment of the pump according to the present invention the slides 5 and *6 arranged in the rotor are guided automatically by the constant contact with the inner and the outer wall defining the stator space in such a manner that no centrifugal moments can cause a sudden reversal of movement of the slides regardless of the speed at which the pump is driven. Thus for the first time it has become possible to increase the output of the pump by increasing the speed thereof and by coupling the rotor of the pump directly to an electric motor. Furthermore a two-stage pump is obtained by the present invention which is formed by one and the same stator and one and the sarhe rotor which is a decided improvement and simplification as compared to other known devices. In particular this pump has an exceptionally high output capacity in relation to its overall dimensions. The sealing-oft" of the pump spaces towards the atmosphere is exceptionally simple 'in the pump described for the reason that the cover wall 3 and the insert or transverse wall 12 of the stator casing respectively, are located below the oil bath of the ejection space. On the other hand the overhung construction of the rotor demands only a single shaft seal 22.

Although only one specific embodiment of the invention has been described and shown in the drawing, it should be noted that the invention may be realized in modified form and adaptations of the arrangement herein disclosed may be made as may readily occur to persons skilled in the art without constituting a departure from the spirit and scope of the invention as defined in the objects and in the appended claims.

What I claim and wish to secure by Letters Patent is:

l. A multi-stage vacuum pump comprising, in combination, a hollow cylindrical stator housing provided with intake opening and exhaust opening, respectively, first, second, and third transverse walls, respectively, extending substantially perpendicular to the axis of and connected to said stator housing, a rotor supported by said first transverse wall and provided with a cylindrical chamber having an open end, said rotor being disposed within said hollow cylindrical stator housing and being eccentrically journalled with respect to the axis of said stator housing, said second transverse wall being provided with ducts and retaining said rotor at said open end in position in said stator housing and being provided with an extension chamber positioned concentrically to said axis of said stator housing and projecting into said rotor chamber to thereby provide a plurality of interspace chambers between upright walls defining, respectively, said stator housing, said rotor chamber and said extension chamber, a plurality of slides disposed in slots passing through the upright wall of said rotor chamber and in contact with the inner wall surface of said stator housing and the outer surface of the wall of said extension chamber, said third transverse wall being provided with passage means establish ing communication through said ducts provided in said 'secend'transverse Wall 'With said interspace "chambers, and normally closed valve means on said third transverse wall regulating the passage of a medium from said intake opening through said interspace chambers, said passage means and said ducts to said exhaust opening, said slides defining pressure and suction spaces during rotation of said rotor relative to said stator housing and said extension chamber, whereby the outer wall surface of said rotor chamber contacts the inner wall surface of said stator housing and said outer wall surface of said extension chamber contacts said inner wall surface of said rotor chamber during said rotation.

2. A multi-stage vacuum pump comprising, in combination, a hollow cylindrical stator housing provided with intake opening for connection with a receptacle and exhaust opening, first, second, and third transverse walls, respectively, extending substantially across the axis of said stator housing, a rotor provided with a cylindrical chamber, said rotor being disposed in spaced relation to the inner wall surface of said stator housing therewithin and being eccentrically journalled on said first transverse wall with respect to the axis of said stator housing, said second transverse wall retaining said rotor within said stator housing and being provided with a cylindrical extension chamber projecting into and spaced from said rotor chamber to thereby provide respective interspace chambers between upright walls defining, respectively, said stator housing, said rotor chamber, and said extension chamber, a plurality "of slide means having cylindrical end faces and disposed in 'slots passing through the upright wall :of said rotor chamber and in contact with the inner cylindrical 'wall surface of said stator housing and the outer cylinder surface of said wall of said extension chamber, to thereby transform said interspace chambers to pressure and suction spaces, respectively, said second and said third transverse walls being provided with respective passageways interconnecting one of said interspace chambers between said stator housing and said rotor on one side of the latter and another of said interspace chambers between said extension chamber and said rotor on the other side of the latter, and normally closed valve means positioned on said third transverse wall for controlling'said passageways during rotation of said rotor thereby establishing direct connection of said one interspace chamber through said exhaust opening with the atmosphere at predetermined pressure in said one interspace chamber.

3. A niul-ti-stage vacuum pump comprising, in combination, 'a hollow cylindrical stator housing provided with inlet means for connection with a receptacle and exhaust means, first, second, and third transverse walls, respectively, extending substantially across the axis of said stator housing, a rotor provided with a cylindrical chamber, said rotor being disposed in spaced relation to the inner wall surface of'sa'id stator housing therewithin and being e'ccentrically journalled on said first transverse wall with respect to the axis of said stator housing, said second transverse wall retaining said rotor in position within said stator housing and supporting a cylindrical extension chamber projecting'into and spaced from said rotor chamber to thereby provide respective interspace chambers between upright walls defining, respectively, said stator housing, said rotor chamber, and 'saidextension chamber, a plurality of slide means having cylindrical end faces and disposed in slots passing through the upright wall of said rotor chamber and in linear contact with the inner cylindrical wall surface of said stator housing and the outer cylindrical surface of said wall of said extension chamber, to thereby transform said interspace chambers to pressure and suction compartments, respectively, said second and said third transverse walls being provided with respective passageways interconnecting one of said interspace chambers between said-stator housing and said rotor on one side of the -latter and another of said interspace chambers between said extension chamber and said rotor on the other side of the latter, and respective normally closed valve means positioned on said third transverse wall and controlling said passageways during rotation of said rotor thereby establishing at one of said valve means direct connection of said pressure compartment with one exhaust means at predetermined pressure in said one interspace chamber and providing at the other valve means connection of said other interspace chamber with another exhaust means when the pressure in said other interspace chamber has reached a predetermined amount.

4. A vacuum pump according to claim 3, wherein said stator housing extends beyond said third transverse wall and forms an ejection chamber for receiving a lubricant, and conduit means extendings centrally through said second and third transverse walls from said eject-ion chamber into the interior of said extension chamber, said extension chamber forming an intermediate reservoir for said lubricant.

5. A vacuum pump according to claim 4, wherein said extension chamber is provided with an overflow opening for lubricant collected in said extension chamber.

6. A vacuum pump according to claim 4, wherein said valve means are immersed within said lubricant when received in said reservoir ejection chamber.

7. A vacuum pump according to claim 4, said conduit means being in the form of a drip pipe to retard escape of lubricant when contained in said reservoir ejection chamber.

8. A vacuum pump according to claim 4, including further means leading from said extension chamber to the outside of said rotor and effectuating for the latter circulation of said lubricant.

9. A vacuum pump according to claim 3, wherein said rotor is provided with an axle journalled in said first transverse wall and extending substantially parallel to the axis of said stator housing, the latter being arranged concentrically to the extension chamber.

References Cited in the file of this patent UNITED STATES PATENTS 232,559 Smith Sept. 21, 1880 462,453 Richmann Nov. 3, 1891 848,446 Crowell Mar. 26, 1907 1,237,668 Machlet Aug. 21, 1917 1,468,889 Trotter Sept. 25, 1923 1,607,383 Aurand Nov. 16, 1926 1,648,885 Seitz Nov. 8, 1927 2,077,394 Buenger Apr. 20, 1937 2,126,553 Hornberger Aug. 9, 1938 2,368,572 Say Jan. 30, 1945 FOREIGN PATENTS 80,874 Switzerland Oct. 18, 1918 264,235 Italy Feb. 1, 1927 

